text: // SPDX-License-Identifier: GPL-2.0+
  /*
   * NILFS B-tree.
   *
   * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
   *
   * Written by Koji Sato.
   */
  
  #include <linux/slab.h>
  #include <linux/string.h>
  #include <linux/errno.h>
  #include <linux/pagevec.h>
  #include "nilfs.h"
  #include "page.h"
  #include "btnode.h"
  #include "btree.h"
  #include "alloc.h"
  #include "dat.h"
  
  static void __nilfs_btree_init(struct nilfs_bmap *bmap);
  
  static struct nilfs_btree_path *nilfs_btree_alloc_path(void)
  {
  	struct nilfs_btree_path *path;
  	int level = NILFS_BTREE_LEVEL_DATA;
  
  	path = kmem_cache_alloc(nilfs_btree_path_cache, GFP_NOFS);
  	if (path == NULL)
  		goto out;
  
  	for (; level < NILFS_BTREE_LEVEL_MAX; level++) {
  		path[level].bp_bh = NULL;
  		path[level].bp_sib_bh = NULL;
  		path[level].bp_index = 0;
  		path[level].bp_oldreq.bpr_ptr = NILFS_BMAP_INVALID_PTR;
  		path[level].bp_newreq.bpr_ptr = NILFS_BMAP_INVALID_PTR;
  		path[level].bp_op = NULL;
  	}
  
  out:
  	return path;
  }
  
  static void nilfs_btree_free_path(struct nilfs_btree_path *path)
  {
  	int level = NILFS_BTREE_LEVEL_DATA;
  
  	for (; level < NILFS_BTREE_LEVEL_MAX; level++)
  		brelse(path[level].bp_bh);
  
  	kmem_cache_free(nilfs_btree_path_cache, path);
  }
  
  /*
   * B-tree node operations
   */
  static int nilfs_btree_get_new_block(const struct nilfs_bmap *btree,
  				     __u64 ptr, struct buffer_head **bhp)
  {
  	struct address_space *btnc = &NILFS_BMAP_I(btree)->i_btnode_cache;
  	struct buffer_head *bh;
  
  	bh = nilfs_btnode_create_block(btnc, ptr);
  	if (!bh)
  		return -ENOMEM;
  
  	set_buffer_nilfs_volatile(bh);
  	*bhp = bh;
  	return 0;
  }
  
  static int nilfs_btree_node_get_flags(const struct nilfs_btree_node *node)
  {
  	return node->bn_flags;
  }
  
  static void
  nilfs_btree_node_set_flags(struct nilfs_btree_node *node, int flags)
  {
  	node->bn_flags = flags;
  }
  
  static int nilfs_btree_node_root(const struct nilfs_btree_node *node)
  {
  	return nilfs_btree_node_get_flags(node) & NILFS_BTREE_NODE_ROOT;
  }
  
  static int nilfs_btree_node_get_level(const struct nilfs_btree_node *node)
  {
  	return node->bn_level;
  }
  
  static void
  nilfs_btree_node_set_level(struct nilfs_btree_node *node, int level)
  {
  	node->bn_level = level;
  }
  
  static int nilfs_btree_node_get_nchildren(const struct nilfs_btree_node *node)
  {
  	return le16_to_cpu(node->bn_nchildren);
  }
  
  static void
  nilfs_btree_node_set_nchildren(struct nilfs_btree_node *node, int nchildren)
  {
  	node->bn_nchildren = cpu_to_le16(nchildren);
  }
  
  static int nilfs_btree_node_size(const struct nilfs_bmap *btree)
  {
  	return i_blocksize(btree->b_inode);
  }
  
  static int nilfs_btree_nchildren_per_block(const struct nilfs_bmap *btree)
  {
  	return btree->b_nchildren_per_block;
  }
  
  static __le64 *
  nilfs_btree_node_dkeys(const struct nilfs_btree_node *node)
  {
  	return (__le64 *)((char *)(node + 1) +
  			  (nilfs_btree_node_root(node) ?
  			   0 : NILFS_BTREE_NODE_EXTRA_PAD_SIZE));
  }
  
  static __le64 *
  nilfs_btree_node_dptrs(const struct nilfs_btree_node *node, int ncmax)
  {
  	return (__le64 *)(nilfs_btree_node_dkeys(node) + ncmax);
  }
  
  static __u64
  nilfs_btree_node_get_key(const struct nilfs_btree_node *node, int index)
  {
  	return le64_to_cpu(*(nilfs_btree_node_dkeys(node) + index));
  }
  
  static void
  nilfs_btree_node_set_key(struct nilfs_btree_node *node, int index, __u64 key)
  {
  	*(nilfs_btree_node_dkeys(node) + index) = cpu_to_le64(key);
  }
  
  static __u64
  nilfs_btree_node_get_ptr(const struct nilfs_btree_node *node, int index,
  			 int ncmax)
  {
  	return le64_to_cpu(*(nilfs_btree_node_dptrs(node, ncmax) + index));
  }
  
  static void
  nilfs_btree_node_set_ptr(struct nilfs_btree_node *node, int index, __u64 ptr,
  			 int ncmax)
  {
  	*(nilfs_btree_node_dptrs(node, ncmax) + index) = cpu_to_le64(ptr);
  }
  
  static void nilfs_btree_node_init(struct nilfs_btree_node *node, int flags,
  				  int level, int nchildren, int ncmax,
  				  const __u64 *keys, const __u64 *ptrs)
  {
  	__le64 *dkeys;
  	__le64 *dptrs;
  	int i;
  
  	nilfs_btree_node_set_flags(node, flags);
  	nilfs_btree_node_set_level(node, level);
  	nilfs_btree_node_set_nchildren(node, nchildren);
  
  	dkeys = nilfs_btree_node_dkeys(node);
  	dptrs = nilfs_btree_node_dptrs(node, ncmax);
  	for (i = 0; i < nchildren; i++) {
  		dkeys[i] = cpu_to_le64(keys[i]);
  		dptrs[i] = cpu_to_le64(ptrs[i]);
  	}
  }
  
  /* Assume the buffer heads corresponding to left and right are locked. */
  static void nilfs_btree_node_move_left(struct nilfs_btree_node *left,
  				       struct nilfs_btree_node *right,
  				       int n, int lncmax, int rncmax)
  {
  	__le64 *ldkeys, *rdkeys;
  	__le64 *ldptrs, *rdptrs;
  	int lnchildren, rnchildren;
  
  	ldkeys = nilfs_btree_node_dkeys(left);
  	ldptrs = nilfs_btree_node_dptrs(left, lncmax);
  	lnchildren = nilfs_btree_node_get_nchildren(left);
  
  	rdkeys = nilfs_btree_node_dkeys(right);
  	rdptrs = nilfs_btree_node_dptrs(right, rncmax);
  	rnchildren = nilfs_btree_node_get_nchildren(right);
  
  	memcpy(ldkeys + lnchildren, rdkeys, n * sizeof(*rdkeys));
  	memcpy(ldptrs + lnchildren, rdptrs, n * sizeof(*rdptrs));
  	memmove(rdkeys, rdkeys + n, (rnchildren - n) * sizeof(*rdkeys));
  	memmove(rdptrs, rdptrs + n, (rnchildren - n) * sizeof(*rdptrs));
  
  	lnchildren += n;
  	rnchildren -= n;
  	nilfs_btree_node_set_nchildren(left, lnchildren);
  	nilfs_btree_node_set_nchildren(right, rnchildren);
  }
  
  /* Assume that the buffer heads corresponding to left and right are locked. */
  static void nilfs_btree_node_move_right(struct nilfs_btree_node *left,
  					struct nilfs_btree_node *right,
  					int n, int lncmax, int rncmax)
  {
  	__le64 *ldkeys, *rdkeys;
  	__le64 *ldptrs, *rdptrs;
  	int lnchildren, rnchildren;
  
  	ldkeys = nilfs_btree_node_dkeys(left);
  	ldptrs = nilfs_btree_node_dptrs(left, lncmax);
  	lnchildren = nilfs_btree_node_get_nchildren(left);
  
  	rdkeys = nilfs_btree_node_dkeys(right);
  	rdptrs = nilfs_btree_node_dptrs(right, rncmax);
  	rnchildren = nilfs_btree_node_get_nchildren(right);
  
  	memmove(rdkeys + n, rdkeys, rnchildren * sizeof(*rdkeys));
  	memmove(rdptrs + n, rdptrs, rnchildren * sizeof(*rdptrs));
  	memcpy(rdkeys, ldkeys + lnchildren - n, n * sizeof(*rdkeys));
  	memcpy(rdptrs, ldptrs + lnchildren - n, n * sizeof(*rdptrs));
  
  	lnchildren -= n;
  	rnchildren += n;
  	nilfs_btree_node_set_nchildren(left, lnchildren);
  	nilfs_btree_node_set_nchildren(right, rnchildren);
  }
  
  /* Assume that the buffer head corresponding to node is locked. */
  static void nilfs_btree_node_insert(struct nilfs_btree_node *node, int index,
  				    __u64 key, __u64 ptr, int ncmax)
  {
  	__le64 *dkeys;
  	__le64 *dptrs;
  	int nchildren;
  
  	dkeys = nilfs_btree_node_dkeys(node);
  	dptrs = nilfs_btree_node_dptrs(node, ncmax);
  	nchildren = nilfs_btree_node_get_nchildren(node);
  	if (index < nchildren) {
  		memmove(dkeys + index + 1, dkeys + index,
  			(nchildren - index) * sizeof(*dkeys));
  		memmove(dptrs + index + 1, dptrs + index,
  			(nchildren - index) * sizeof(*dptrs));
  	}
  	dkeys[index] = cpu_to_le64(key);
  	dptrs[index] = cpu_to_le64(ptr);
  	nchildren++;
  	nilfs_btree_node_set_nchildren(node, nchildren);
  }
  
  /* Assume that the buffer head corresponding to node is locked. */
  static void nilfs_btree_node_delete(struct nilfs_btree_node *node, int index,
  				    __u64 *keyp, __u64 *ptrp, int ncmax)
  {
  	__u64 key;
  	__u64 ptr;
  	__le64 *dkeys;
  	__le64 *dptrs;
  	int nchildren;
  
  	dkeys = nilfs_btree_node_dkeys(node);
  	dptrs = nilfs_btree_node_dptrs(node, ncmax);
  	key = le64_to_cpu(dkeys[index]);
  	ptr = le64_to_cpu(dptrs[index]);
  	nchildren = nilfs_btree_node_get_nchildren(node);
  	if (keyp != NULL)
  		*keyp = key;
  	if (ptrp != NULL)
  		*ptrp = ptr;
  
  	if (index < nchildren - 1) {
  		memmove(dkeys + index, dkeys + index + 1,
  			(nchildren - index - 1) * sizeof(*dkeys));
  		memmove(dptrs + index, dptrs + index + 1,
  			(nchildren - index - 1) * sizeof(*dptrs));
  	}
  	nchildren--;
  	nilfs_btree_node_set_nchildren(node, nchildren);
  }
  
  static int nilfs_btree_node_lookup(const struct nilfs_btree_node *node,
  				   __u64 key, int *indexp)
  {
  	__u64 nkey;
  	int index, low, high, s;
  
  	/* binary search */
  	low = 0;
  	high = nilfs_btree_node_get_nchildren(node) - 1;
  	index = 0;
  	s = 0;
  	while (low <= high) {
  		index = (low + high) / 2;
  		nkey = nilfs_btree_node_get_key(node, index);
  		if (nkey == key) {
  			s = 0;
  			goto out;
  		} else if (nkey < key) {
  			low = index + 1;
  			s = -1;
  		} else {
  			high = index - 1;
  			s = 1;
  		}
  	}
  
  	/* adjust index */
  	if (nilfs_btree_node_get_level(node) > NILFS_BTREE_LEVEL_NODE_MIN) {
  		if (s > 0 && index > 0)
  			index--;
  	} else if (s < 0)
  		index++;
  
   out:
  	*indexp = index;
  
  	return s == 0;
  }
  
  /**
   * nilfs_btree_node_broken - verify consistency of btree node
   * @node: btree node block to be examined
   * @size: node size (in bytes)
   * @inode: host inode of btree
   * @blocknr: block number
   *
   * Return Value: If node is broken, 1 is returned. Otherwise, 0 is returned.
   */
  static int nilfs_btree_node_broken(const struct nilfs_btree_node *node,
  				   size_t size, struct inode *inode,
  				   sector_t blocknr)
  {
  	int level, flags, nchildren;
  	int ret = 0;
  
  	level = nilfs_btree_node_get_level(node);
  	flags = nilfs_btree_node_get_flags(node);
  	nchildren = nilfs_btree_node_get_nchildren(node);
  
  	if (unlikely(level < NILFS_BTREE_LEVEL_NODE_MIN ||
  		     level >= NILFS_BTREE_LEVEL_MAX ||
  		     (flags & NILFS_BTREE_NODE_ROOT) ||
  		     nchildren < 0 ||
  		     nchildren > NILFS_BTREE_NODE_NCHILDREN_MAX(size))) {
  		nilfs_crit(inode->i_sb,
  			   "bad btree node (ino=%lu, blocknr=%llu): level = %d, flags = 0x%x, nchildren = %d",
  			   inode->i_ino, (unsigned long long)blocknr, level,
  			   flags, nchildren);
  		ret = 1;
  	}
  	return ret;
  }
  
  /**
   * nilfs_btree_root_broken - verify consistency of btree root node
   * @node: btree root node to be examined
   * @inode: host inode of btree
   *
   * Return Value: If node is broken, 1 is returned. Otherwise, 0 is returned.
   */
  static int nilfs_btree_root_broken(const struct nilfs_btree_node *node,
  				   struct inode *inode)
  {
  	int level, flags, nchildren;
  	int ret = 0;
  
  	level = nilfs_btree_node_get_level(node);
  	flags = nilfs_btree_node_get_flags(node);
  	nchildren = nilfs_btree_node_get_nchildren(node);
  
  	if (unlikely(level < NILFS_BTREE_LEVEL_NODE_MIN ||
  		     level >= NILFS_BTREE_LEVEL_MAX ||
  		     nchildren < 0 ||
  		     nchildren > NILFS_BTREE_ROOT_NCHILDREN_MAX)) {
  		nilfs_crit(inode->i_sb,
  			   "bad btree root (ino=%lu): level = %d, flags = 0x%x, nchildren = %d",
  			   inode->i_ino, level, flags, nchildren);
  		ret = 1;
  	}
  	return ret;
  }
  
  int nilfs_btree_broken_node_block(struct buffer_head *bh)
  {
  	struct inode *inode;
  	int ret;
  
  	if (buffer_nilfs_checked(bh))
  		return 0;
  
  	inode = bh->b_page->mapping->host;
  	ret = nilfs_btree_node_broken((struct nilfs_btree_node *)bh->b_data,
  				      bh->b_size, inode, bh->b_blocknr);
  	if (likely(!ret))
  		set_buffer_nilfs_checked(bh);
  	return ret;
  }
  
  static struct nilfs_btree_node *
  nilfs_btree_get_root(const struct nilfs_bmap *btree)
  {
  	return (struct nilfs_btree_node *)btree->b_u.u_data;
  }
  
  static struct nilfs_btree_node *
  nilfs_btree_get_nonroot_node(const struct nilfs_btree_path *path, int level)
  {
  	return (struct nilfs_btree_node *)path[level].bp_bh->b_data;
  }
  
  static struct nilfs_btree_node *
  nilfs_btree_get_sib_node(const struct nilfs_btree_path *path, int level)
  {
  	return (struct nilfs_btree_node *)path[level].bp_sib_bh->b_data;
  }
  
  static int nilfs_btree_height(const struct nilfs_bmap *btree)
  {
  	return nilfs_btree_node_get_level(nilfs_btree_get_root(btree)) + 1;
  }
  
  static struct nilfs_btree_node *
  nilfs_btree_get_node(const struct nilfs_bmap *btree,
  		     const struct nilfs_btree_path *path,
  		     int level, int *ncmaxp)
  {
  	struct nilfs_btree_node *node;
  
  	if (level == nilfs_btree_height(btree) - 1) {
  		node = nilfs_btree_get_root(btree);
  		*ncmaxp = NILFS_BTREE_ROOT_NCHILDREN_MAX;
  	} else {
  		node = nilfs_btree_get_nonroot_node(path, level);
  		*ncmaxp = nilfs_btree_nchildren_per_block(btree);
  	}
  	return node;
  }
  
  static int nilfs_btree_bad_node(const struct nilfs_bmap *btree,
  				struct nilfs_btree_node *node, int level)
  {
  	if (unlikely(nilfs_btree_node_get_level(node) != level)) {
  		dump_stack();
  		nilfs_crit(btree->b_inode->i_sb,
  			   "btree level mismatch (ino=%lu): %d != %d",
  			   btree->b_inode->i_ino,
  			   nilfs_btree_node_get_level(node), level);
  		return 1;
  	}
  	return 0;
  }
  
  struct nilfs_btree_readahead_info {
  	struct nilfs_btree_node *node;	/* parent node */
  	int max_ra_blocks;		/* max nof blocks to read ahead */
  	int index;			/* current index on the parent node */
  	int ncmax;			/* nof children in the parent node */
  };
  
  static int __nilfs_btree_get_block(const struct nilfs_bmap *btree, __u64 ptr,
  				   struct buffer_head **bhp,
  				   const struct nilfs_btree_readahead_info *ra)
  {
  	struct address_space *btnc = &NILFS_BMAP_I(btree)->i_btnode_cache;
  	struct buffer_head *bh, *ra_bh;
  	sector_t submit_ptr = 0;
  	int ret;
  
  	ret = nilfs_btnode_submit_block(btnc, ptr, 0, REQ_OP_READ, 0, &bh,
  					&submit_ptr);
  	if (ret) {
  		if (ret != -EEXIST)
  			return ret;
  		goto out_check;
  	}
  
  	if (ra) {
  		int i, n;
  		__u64 ptr2;
  
  		/* read ahead sibling nodes */
  		for (n = ra->max_ra_blocks, i = ra->index + 1;
  		     n > 0 && i < ra->ncmax; n--, i++) {
  			ptr2 = nilfs_btree_node_get_ptr(ra->node, i, ra->ncmax);
  
  			ret = nilfs_btnode_submit_block(btnc, ptr2, 0,
  							REQ_OP_READ, REQ_RAHEAD,
  							&ra_bh, &submit_ptr);
  			if (likely(!ret || ret == -EEXIST))
  				brelse(ra_bh);
  			else if (ret != -EBUSY)
  				break;
  			if (!buffer_locked(bh))
  				goto out_no_wait;
  		}
  	}
  
  	wait_on_buffer(bh);
  
   out_no_wait:
  	if (!buffer_uptodate(bh)) {
  		nilfs_err(btree->b_inode->i_sb,
  			  "I/O error reading b-tree node block (ino=%lu, blocknr=%llu)",
  			  btree->b_inode->i_ino, (unsigned long long)ptr);
  		brelse(bh);
  		return -EIO;
  	}
  
   out_check:
  	if (nilfs_btree_broken_node_block(bh)) {
  		clear_buffer_uptodate(bh);
  		brelse(bh);
  		return -EINVAL;
  	}
  
  	*bhp = bh;
  	return 0;
  }
  
  static int nilfs_btree_get_block(const struct nilfs_bmap *btree, __u64 ptr,
  				   struct buffer_head **bhp)
  {
  	return __nilfs_btree_get_block(btree, ptr, bhp, NULL);
  }
  
  static int nilfs_btree_do_lookup(const struct nilfs_bmap *btree,
  				 struct nilfs_btree_path *path,
  				 __u64 key, __u64 *ptrp, int minlevel,
  				 int readahead)
  {
  	struct nilfs_btree_node *node;
  	struct nilfs_btree_readahead_info p, *ra;
  	__u64 ptr;
  	int level, index, found, ncmax, ret;
  
  	node = nilfs_btree_get_root(btree);
  	level = nilfs_btree_node_get_level(node);
  	if (level < minlevel || nilfs_btree_node_get_nchildren(node) <= 0)
  		return -ENOENT;
  
  	found = nilfs_btree_node_lookup(node, key, &index);
  	ptr = nilfs_btree_node_get_ptr(node, index,
  				       NILFS_BTREE_ROOT_NCHILDREN_MAX);
  	path[level].bp_bh = NULL;
  	path[level].bp_index = index;
  
  	ncmax = nilfs_btree_nchildren_per_block(btree);
  
  	while (--level >= minlevel) {
  		ra = NULL;
  		if (level == NILFS_BTREE_LEVEL_NODE_MIN && readahead) {
  			p.node = nilfs_btree_get_node(btree, path, level + 1,
  						      &p.ncmax);
  			p.index = index;
  			p.max_ra_blocks = 7;
  			ra = &p;
  		}
  		ret = __nilfs_btree_get_block(btree, ptr, &path[level].bp_bh,
  					      ra);
  		if (ret < 0)
  			return ret;
  
  		node = nilfs_btree_get_nonroot_node(path, level);
  		if (nilfs_btree_bad_node(btree, node, level))
  			return -EINVAL;
  		if (!found)
  			found = nilfs_btree_node_lookup(node, key, &index);
  		else
  			index = 0;
  		if (index < ncmax) {
  			ptr = nilfs_btree_node_get_ptr(node, index, ncmax);
  		} else {
  			WARN_ON(found || level != NILFS_BTREE_LEVEL_NODE_MIN);
  			/* insert */
  			ptr = NILFS_BMAP_INVALID_PTR;
  		}
  		path[level].bp_index = index;
  	}
  	if (!found)
  		return -ENOENT;
  
  	if (ptrp != NULL)
  		*ptrp = ptr;
  
  	return 0;
  }
  
  static int nilfs_btree_do_lookup_last(const struct nilfs_bmap *btree,
  				      struct nilfs_btree_path *path,
  				      __u64 *keyp, __u64 *ptrp)
  {
  	struct nilfs_btree_node *node;
  	__u64 ptr;
  	int index, level, ncmax, ret;
  
  	node = nilfs_btree_get_root(btree);
  	index = nilfs_btree_node_get_nchildren(node) - 1;
  	if (index < 0)
  		return -ENOENT;
  	level = nilfs_btree_node_get_level(node);
  	ptr = nilfs_btree_node_get_ptr(node, index,
  				       NILFS_BTREE_ROOT_NCHILDREN_MAX);
  	path[level].bp_bh = NULL;
  	path[level].bp_index = index;
  	ncmax = nilfs_btree_nchildren_per_block(btree);
  
  	for (level--; level > 0; level--) {
  		ret = nilfs_btree_get_block(btree, ptr, &path[level].bp_bh);
  		if (ret < 0)
  			return ret;
  		node = nilfs_btree_get_nonroot_node(path, level);
  		if (nilfs_btree_bad_node(btree, node, level))
  			return -EINVAL;
  		index = nilfs_btree_node_get_nchildren(node) - 1;
  		ptr = nilfs_btree_node_get_ptr(node, index, ncmax);
  		path[level].bp_index = index;
  	}
  
  	if (keyp != NULL)
  		*keyp = nilfs_btree_node_get_key(node, index);
  	if (ptrp != NULL)
  		*ptrp = ptr;
  
  	return 0;
  }
  
  /**
   * nilfs_btree_get_next_key - get next valid key from btree path array
   * @btree: bmap struct of btree
   * @path: array of nilfs_btree_path struct
   * @minlevel: start level
   * @nextkey: place to store the next valid key
   *
   * Return Value: If a next key was found, 0 is returned. Otherwise,
   * -ENOENT is returned.
   */
  static int nilfs_btree_get_next_key(const struct nilfs_bmap *btree,
  				    const struct nilfs_btree_path *path,
  				    int minlevel, __u64 *nextkey)
  {
  	struct nilfs_btree_node *node;
  	int maxlevel = nilfs_btree_height(btree) - 1;
  	int index, next_adj, level;
  
  	/* Next index is already set to bp_index for leaf nodes. */
  	next_adj = 0;
  	for (level = minlevel; level <= maxlevel; level++) {
  		if (level == maxlevel)
  			node = nilfs_btree_get_root(btree);
  		else
  			node = nilfs_btree_get_nonroot_node(path, level);
  
  		index = path[level].bp_index + next_adj;
  		if (index < nilfs_btree_node_get_nchildren(node)) {
  			/* Next key is in this node */
  			*nextkey = nilfs_btree_node_get_key(node, index);
  			return 0;
  		}
  		/* For non-leaf nodes, next index is stored at bp_index + 1. */
  		next_adj = 1;
  	}
  	return -ENOENT;
  }
  
  static int nilfs_btree_lookup(const struct nilfs_bmap *btree,
  			      __u64 key, int level, __u64 *ptrp)
  {
  	struct nilfs_btree_path *path;
  	int ret;
  
  	path = nilfs_btree_alloc_path();
  	if (path == NULL)
  		return -ENOMEM;
  
  	ret = nilfs_btree_do_lookup(btree, path, key, ptrp, level, 0);
  
  	nilfs_btree_free_path(path);
  
  	return ret;
  }
  
  static int nilfs_btree_lookup_contig(const struct nilfs_bmap *btree,
  				     __u64 key, __u64 *ptrp,
  				     unsigned int maxblocks)
  {
  	struct nilfs_btree_path *path;
  	struct nilfs_btree_node *node;
  	struct inode *dat = NULL;
  	__u64 ptr, ptr2;
  	sector_t blocknr;
  	int level = NILFS_BTREE_LEVEL_NODE_MIN;
  	int ret, cnt, index, maxlevel, ncmax;
  	struct nilfs_btree_readahead_info p;
  
  	path = nilfs_btree_alloc_path();
  	if (path == NULL)
  		return -ENOMEM;
  
  	ret = nilfs_btree_do_lookup(btree, path, key, &ptr, level, 1);
  	if (ret < 0)
  		goto out;
  
  	if (NILFS_BMAP_USE_VBN(btree)) {
  		dat = nilfs_bmap_get_dat(btree);
  		ret = nilfs_dat_translate(dat, ptr, &blocknr);
  		if (ret < 0)
  			goto out;
  		ptr = blocknr;
  	}
  	cnt = 1;
  	if (cnt == maxblocks)
  		goto end;
  
  	maxlevel = nilfs_btree_height(btree) - 1;
  	node = nilfs_btree_get_node(btree, path, level, &ncmax);
  	index = path[level].bp_index + 1;
  	for (;;) {
  		while (index < nilfs_btree_node_get_nchildren(node)) {
  			if (nilfs_btree_node_get_key(node, index) !=
  			    key + cnt)
  				goto end;
  			ptr2 = nilfs_btree_node_get_ptr(node, index, ncmax);
  			if (dat) {
  				ret = nilfs_dat_translate(dat, ptr2, &blocknr);
  				if (ret < 0)
  					goto out;
  				ptr2 = blocknr;
  			}
  			if (ptr2 != ptr + cnt || ++cnt == maxblocks)
  				goto end;
  			index++;
  		}
  		if (level == maxlevel)
  			break;
  
  		/* look-up right sibling node */
  		p.node = nilfs_btree_get_node(btree, path, level + 1, &p.ncmax);
  		p.index = path[level + 1].bp_index + 1;
  		p.max_ra_blocks = 7;
  		if (p.index >= nilfs_btree_node_get_nchildren(p.node) ||
  		    nilfs_btree_node_get_key(p.node, p.index) != key + cnt)
  			break;
  		ptr2 = nilfs_btree_node_get_ptr(p.node, p.index, p.ncmax);
  		path[level + 1].bp_index = p.index;
  
  		brelse(path[level].bp_bh);
  		path[level].bp_bh = NULL;
  
  		ret = __nilfs_btree_get_block(btree, ptr2, &path[level].bp_bh,
  					      &p);
  		if (ret < 0)
  			goto out;
  		node = nilfs_btree_get_nonroot_node(path, level);
  		ncmax = nilfs_btree_nchildren_per_block(btree);
  		index = 0;
  		path[level].bp_index = index;
  	}
   end:
  	*ptrp = ptr;
  	ret = cnt;
   out:
  	nilfs_btree_free_path(path);
  	return ret;
  }
  
  static void nilfs_btree_promote_key(struct nilfs_bmap *btree,
  				    struct nilfs_btree_path *path,
  				    int level, __u64 key)
  {
  	if (level < nilfs_btree_height(btree) - 1) {
  		do {
  			nilfs_btree_node_set_key(
  				nilfs_btree_get_nonroot_node(path, level),
  				path[level].bp_index, key);
  			if (!buffer_dirty(path[level].bp_bh))
  				mark_buffer_dirty(path[level].bp_bh);
  		} while ((path[level].bp_index == 0) &&
  			 (++level < nilfs_btree_height(btree) - 1));
  	}
  
  	/* root */
  	if (level == nilfs_btree_height(btree) - 1) {
  		nilfs_btree_node_set_key(nilfs_btree_get_root(btree),
  					 path[level].bp_index, key);
  	}
  }
  
  static void nilfs_btree_do_insert(struct nilfs_bmap *btree,
  				  struct nilfs_btree_path *path,
  				  int level, __u64 *keyp, __u64 *ptrp)
  {
  	struct nilfs_btree_node *node;
  	int ncblk;
  
  	if (level < nilfs_btree_height(btree) - 1) {
  		node = nilfs_btree_get_nonroot_node(path, level);
  		ncblk = nilfs_btree_nchildren_per_block(btree);
  		nilfs_btree_node_insert(node, path[level].bp_index,
  					*keyp, *ptrp, ncblk);
  		if (!buffer_dirty(path[level].bp_bh))
  			mark_buffer_dirty(path[level].bp_bh);
  
  		if (path[level].bp_index == 0)
  			nilfs_btree_promote_key(btree, path, level + 1,
  						nilfs_btree_node_get_key(node,
  									 0));
  	} else {
  		node = nilfs_btree_get_root(btree);
  		nilfs_btree_node_insert(node, path[level].bp_index,
  					*keyp, *ptrp,
  					NILFS_BTREE_ROOT_NCHILDREN_MAX);
  	}
  }
  
  static void nilfs_btree_carry_left(struct nilfs_bmap *btree,
  				   struct nilfs_btree_path *path,
  				   int level, __u64 *keyp, __u64 *ptrp)
  {
  	struct nilfs_btree_node *node, *left;
  	int nchildren, lnchildren, n, move, ncblk;
  
  	node = nilfs_btree_get_nonroot_node(path, level);
  	left = nilfs_btree_get_sib_node(path, level);
  	nchildren = nilfs_btree_node_get_nchildren(node);
  	lnchildren = nilfs_btree_node_get_nchildren(left);
  	ncblk = nilfs_btree_nchildren_per_block(btree);
  	move = 0;
  
  	n = (nchildren + lnchildren + 1) / 2 - lnchildren;
  	if (n > path[level].bp_index) {
  		/* move insert point */
  		n--;
  		move = 1;
  	}
  
  	nilfs_btree_node_move_left(left, node, n, ncblk, ncblk);
  
  	if (!buffer_dirty(path[level].bp_bh))
  		mark_buffer_dirty(path[level].bp_bh);
  	if (!buffer_dirty(path[level].bp_sib_bh))
  		mark_buffer_dirty(path[level].bp_sib_bh);
  
  	nilfs_btree_promote_key(btree, path, level + 1,
  				nilfs_btree_node_get_key(node, 0));
  
  	if (move) {
  		brelse(path[level].bp_bh);
  		path[level].bp_bh = path[level].bp_sib_bh;
  		path[level].bp_sib_bh = NULL;
  		path[level].bp_index += lnchildren;
  		path[level + 1].bp_index--;
  	} else {
  		brelse(path[level].bp_sib_bh);
  		path[level].bp_sib_bh = NULL;
  		path[level].bp_index -= n;
  	}
  
  	nilfs_btree_do_insert(btree, path, level, keyp, ptrp);
  }
  
  static void nilfs_btree_carry_right(struct nilfs_bmap *btree,
  				    struct nilfs_btree_path *path,
  				    int level, __u64 *keyp, __u64 *ptrp)
  {
  	struct nilfs_btree_node *node, *right;
  	int nchildren, rnchildren, n, move, ncblk;
  
  	node = nilfs_btree_get_nonroot_node(path, level);
  	right = nilfs_btree_get_sib_node(path, level);
  	nchildren = nilfs_btree_node_get_nchildren(node);
  	rnchildren = nilfs_btree_node_get_nchildren(right);
  	ncblk = nilfs_btree_nchildren_per_block(btree);
  	move = 0;
  
  	n = (nchildren + rnchildren + 1) / 2 - rnchildren;
  	if (n > nchildren - path[level].bp_index) {
  		/* move insert point */
  		n--;
  		move = 1;
  	}
  
  	nilfs_btree_node_move_right(node, right, n, ncblk, ncblk);
  
  	if (!buffer_dirty(path[level].bp_bh))
  		mark_buffer_dirty(path[level].bp_bh);
  	if (!buffer_dirty(path[level].bp_sib_bh))
  		mark_buffer_dirty(path[level].bp_sib_bh);
  
  	path[level + 1].bp_index++;
  	nilfs_btree_promote_key(btree, path, level + 1,
  				nilfs_btree_node_get_key(right, 0));
  	path[level + 1].bp_index--;
  
  	if (move) {
  		brelse(path[level].bp_bh);
  		path[level].bp_bh = path[level].bp_sib_bh;
  		path[level].bp_sib_bh = NULL;
  		path[level].bp_index -= nilfs_btree_node_get_nchildren(node);
  		path[level + 1].bp_index++;
  	} else {
  		brelse(path[level].bp_sib_bh);
  		path[level].bp_sib_bh = NULL;
  	}
  
  	nilfs_btree_do_insert(btree, path, level, keyp, ptrp);
  }
  
  static void nilfs_btree_split(struct nilfs_bmap *btree,
  			      struct nilfs_btree_path *path,
  			      int level, __u64 *keyp, __u64 *ptrp)
  {
  	struct nilfs_btree_node *node, *right;
  	int nchildren, n, move, ncblk;
  
  	node = nilfs_btree_get_nonroot_node(path, level);
  	right = nilfs_btree_get_sib_node(path, level);
  	nchildren = nilfs_btree_node_get_nchildren(node);
  	ncblk = nilfs_btree_nchildren_per_block(btree);
  	move = 0;
  
  	n = (nchildren + 1) / 2;
  	if (n > nchildren - path[level].bp_index) {
  		n--;
  		move = 1;
  	}
  
  	nilfs_btree_node_move_right(node, right, n, ncblk, ncblk);
  
  	if (!buffer_dirty(path[level].bp_bh))
  		mark_buffer_dirty(path[level].bp_bh);
  	if (!buffer_dirty(path[level].bp_sib_bh))
  		mark_buffer_dirty(path[level].bp_sib_bh);
  
  	if (move) {
  		path[level].bp_index -= nilfs_btree_node_get_nchildren(node);
  		nilfs_btree_node_insert(right, path[level].bp_index,
  					*keyp, *ptrp, ncblk);
  
  		*keyp = nilfs_btree_node_get_key(right, 0);
  		*ptrp = path[level].bp_newreq.bpr_ptr;
  
  		brelse(path[level].bp_bh);
  		path[level].bp_bh = path[level].bp_sib_bh;
  		path[level].bp_sib_bh = NULL;
  	} else {
  		nilfs_btree_do_insert(btree, path, level, keyp, ptrp);
  
  		*keyp = nilfs_btree_node_get_key(right, 0);
  		*ptrp = path[level].bp_newreq.bpr_ptr;
  
  		brelse(path[level].bp_sib_bh);
  		path[level].bp_sib_bh = NULL;
  	}
  
  	path[level + 1].bp_index++;
  }
  
  static void nilfs_btree_grow(struct nilfs_bmap *btree,
  			     struct nilfs_btree_path *path,
  			     int level, __u64 *keyp, __u64 *ptrp)
  {
  	struct nilfs_btree_node *root, *child;
  	int n, ncblk;
  
  	root = nilfs_btree_get_root(btree);
  	child = nilfs_btree_get_sib_node(path, level);
  	ncblk = nilfs_btree_nchildren_per_block(btree);
  
  	n = nilfs_btree_node_get_nchildren(root);
  
  	nilfs_btree_node_move_right(root, child, n,
  				    NILFS_BTREE_ROOT_NCHILDREN_MAX, ncblk);
  	nilfs_btree_node_set_level(root, level + 1);
  
  	if (!buffer_dirty(path[level].bp_sib_bh))
  		mark_buffer_dirty(path[level].bp_sib_bh);
  
  	path[level].bp_bh = path[level].bp_sib_bh;
  	path[level].bp_sib_bh = NULL;
  
  	nilfs_btree_do_insert(btree, path, level, keyp, ptrp);
  
  	*keyp = nilfs_btree_node_get_key(child, 0);
  	*ptrp = path[level].bp_newreq.bpr_ptr;
  }
  
  static __u64 nilfs_btree_find_near(const struct nilfs_bmap *btree,
  				   const struct nilfs_btree_path *path)
  {
  	struct nilfs_btree_node *node;
  	int level, ncmax;
  
  	if (path == NULL)
  		return NILFS_BMAP_INVALID_PTR;
  
  	/* left sibling */
  	level = NILFS_BTREE_LEVEL_NODE_MIN;
  	if (path[level].bp_index > 0) {
  		node = nilfs_btree_get_node(btree, path, level, &ncmax);
  		return nilfs_btree_node_get_ptr(node,
  						path[level].bp_index - 1,
  						ncmax);
  	}
  
  	/* parent */
  	level = NILFS_BTREE_LEVEL_NODE_MIN + 1;
  	if (level <= nilfs_btree_height(btree) - 1) {
  		node = nilfs_btree_get_node(btree, path, level, &ncmax);
  		return nilfs_btree_node_get_ptr(node, path[level].bp_index,
  						ncmax);
  	}
  
  	return NILFS_BMAP_INVALID_PTR;
  }
  
  static __u64 nilfs_btree_find_target_v(const struct nilfs_bmap *btree,
  				       const struct nilfs_btree_path *path,
  				       __u64 key)
  {
  	__u64 ptr;
  
  	ptr = nilfs_bmap_find_target_seq(btree, key);
  	if (ptr != NILFS_BMAP_INVALID_PTR)
  		/* sequential access */
  		return ptr;
  
  	ptr = nilfs_btree_find_near(btree, path);
  	if (ptr != NILFS_BMAP_INVALID_PTR)
  		/* near */
  		return ptr;
  
  	/* block group */
  	return nilfs_bmap_find_target_in_group(btree);
  }
  
  static int nilfs_btree_prepare_insert(struct nilfs_bmap *btree,
  				      struct nilfs_btree_path *path,
  				      int *levelp, __u64 key, __u64 ptr,
  				      struct nilfs_bmap_stats *stats)
  {
  	struct buffer_head *bh;
  	struct nilfs_btree_node *node, *parent, *sib;
  	__u64 sibptr;
  	int pindex, level, ncmax, ncblk, ret;
  	struct inode *dat = NULL;
  
  	stats->bs_nblocks = 0;
  	level = NILFS_BTREE_LEVEL_DATA;
  
  	/* allocate a new ptr for data block */
  	if (NILFS_BMAP_USE_VBN(btree)) {
  		path[level].bp_newreq.bpr_ptr =
  			nilfs_btree_find_target_v(btree, path, key);
  		dat = nilfs_bmap_get_dat(btree);
  	}
  
  	ret = nilfs_bmap_prepare_alloc_ptr(btree, &path[level].bp_newreq, dat);
  	if (ret < 0)
  		goto err_out_data;
  
  	ncblk = nilfs_btree_nchildren_per_block(btree);
  
  	for (level = NILFS_BTREE_LEVEL_NODE_MIN;
  	     level < nilfs_btree_height(btree) - 1;
  	     level++) {
  		node = nilfs_btree_get_nonroot_node(path, level);
  		if (nilfs_btree_node_get_nchildren(node) < ncblk) {
  			path[level].bp_op = nilfs_btree_do_insert;
  			stats->bs_nblocks++;
  			goto out;
  		}
  
  		parent = nilfs_btree_get_node(btree, path, level + 1, &ncmax);
  		pindex = path[level + 1].bp_index;
  
  		/* left sibling */
  		if (pindex > 0) {
  			sibptr = nilfs_btree_node_get_ptr(parent, pindex - 1,
  							  ncmax);
  			ret = nilfs_btree_get_block(btree, sibptr, &bh);
  			if (ret < 0)
  				goto err_out_child_node;
  			sib = (struct nilfs_btree_node *)bh->b_data;
  			if (nilfs_btree_node_get_nchildren(sib) < ncblk) {
  				path[level].bp_sib_bh = bh;
  				path[level].bp_op = nilfs_btree_carry_left;
  				stats->bs_nblocks++;
  				goto out;
  			} else {
  				brelse(bh);
  			}
  		}
  
  		/* right sibling */
  		if (pindex < nilfs_btree_node_get_nchildren(parent) - 1) {
  			sibptr = nilfs_btree_node_get_ptr(parent, pindex + 1,
  							  ncmax);
  			ret = nilfs_btree_get_block(btree, sibptr, &bh);
  			if (ret < 0)
  				goto err_out_child_node;
  			sib = (struct nilfs_btree_node *)bh->b_data;
  			if (nilfs_btree_node_get_nchildren(sib) < ncblk) {
  				path[level].bp_sib_bh = bh;
  				path[level].bp_op = nilfs_btree_carry_right;
  				stats->bs_nblocks++;
  				goto out;
  			} else {
  				brelse(bh);
  			}
  		}
  
  		/* split */
  		path[level].bp_newreq.bpr_ptr =
  			path[level - 1].bp_newreq.bpr_ptr + 1;
  		ret = nilfs_bmap_prepare_alloc_ptr(btree,
  						   &path[level].bp_newreq, dat);
  		if (ret < 0)
  			goto err_out_child_node;
  		ret = nilfs_btree_get_new_block(btree,
  						path[level].bp_newreq.bpr_ptr,
  						&bh);
  		if (ret < 0)
  			goto err_out_curr_node;
  
  		stats->bs_nblocks++;
  
  		sib = (struct nilfs_btree_node *)bh->b_data;
  		nilfs_btree_node_init(sib, 0, level, 0, ncblk, NULL, NULL);
  		path[level].bp_sib_bh = bh;
  		path[level].bp_op = nilfs_btree_split;
  	}
  
  	/* root */
  	node = nilfs_btree_get_root(btree);
  	if (nilfs_btree_node_get_nchildren(node) <
  	    NILFS_BTREE_ROOT_NCHILDREN_MAX) {
  		path[level].bp_op = nilfs_btree_do_insert;
  		stats->bs_nblocks++;
  		goto out;
  	}
  
  	/* grow */
  	path[level].bp_newreq.bpr_ptr = path[level - 1].bp_newreq.bpr_ptr + 1;
  	ret = nilfs_bmap_prepare_alloc_ptr(btree, &path[level].bp_newreq, dat);
  	if (ret < 0)
  		goto err_out_child_node;
  	ret = nilfs_btree_get_new_block(btree, path[level].bp_newreq.bpr_ptr,
  					&bh);
  	if (ret < 0)
  		goto err_out_curr_node;
  
  	nilfs_btree_node_init((struct nilfs_btree_node *)bh->b_data,
  			      0, level, 0, ncblk, NULL, NULL);
  	path[level].bp_sib_bh = bh;
  	path[level].bp_op = nilfs_btree_grow;
  
  	level++;
  	path[level].bp_op = nilfs_btree_do_insert;
  
  	/* a newly-created node block and a data block are added */
  	stats->bs_nblocks += 2;
  
  	/* success */
   out:
  	*levelp = level;
  	return ret;
  
  	/* error */
   err_out_curr_node:
  	nilfs_bmap_abort_alloc_ptr(btree, &path[level].bp_newreq, dat);
   err_out_child_node:
  	for (level--; level > NILFS_BTREE_LEVEL_DATA; level--) {
  		nilfs_btnode_delete(path[level].bp_sib_bh);
  		nilfs_bmap_abort_alloc_ptr(btree, &path[level].bp_newreq, dat);
  
  	}
  
  	nilfs_bmap_abort_alloc_ptr(btree, &path[level].bp_newreq, dat);
   err_out_data:
  	*levelp = level;
  	stats->bs_nblocks = 0;
  	return ret;
  }
  
  static void nilfs_btree_commit_insert(struct nilfs_bmap *btree,
  				      struct nilfs_btree_path *path,
  				      int maxlevel, __u64 key, __u64 ptr)
  {
  	struct inode *dat = NULL;
  	int level;
  
  	set_buffer_nilfs_volatile((struct buffer_head *)((unsigned long)ptr));
  	ptr = path[NILFS_BTREE_LEVEL_DATA].bp_newreq.bpr_ptr;
  	if (NILFS_BMAP_USE_VBN(btree)) {
  		nilfs_bmap_set_target_v(btree, key, ptr);
  		dat = nilfs_bmap_get_dat(btree);
  	}
  
  	for (level = NILFS_BTREE_LEVEL_NODE_MIN; level <= maxlevel; level++) {
  		nilfs_bmap_commit_alloc_ptr(btree,
  					    &path[level - 1].bp_newreq, dat);
  		path[level].bp_op(btree, path, level, &key, &ptr);
  	}
  
  	if (!nilfs_bmap_dirty(btree))
  		nilfs_bmap_set_dirty(btree);
  }
  
  static int nilfs_btree_insert(struct nilfs_bmap *btree, __u64 key, __u64 ptr)
  {
  	struct nilfs_btree_path *path;
  	struct nilfs_bmap_stats stats;
  	int level, ret;
  
  	path = nilfs_btree_alloc_path();
  	if (path == NULL)
  		return -ENOMEM;
  
  	ret = nilfs_btree_do_lookup(btree, path, key, NULL,
  				    NILFS_BTREE_LEVEL_NODE_MIN, 0);
  	if (ret != -ENOENT) {
  		if (ret == 0)
  			ret = -EEXIST;
  		goto out;
  	}
  
  	ret = nilfs_btree_prepare_insert(btree, path, &level, key, ptr, &stats);
  	if (ret < 0)
  		goto out;
  	nilfs_btree_commit_insert(btree, path, level, key, ptr);
  	nilfs_inode_add_blocks(btree->b_inode, stats.bs_nblocks);
  
   out:
  	nilfs_btree_free_path(path);
  	return ret;
  }
  
  static void nilfs_btree_do_delete(struct nilfs_bmap *btree,
  				  struct nilfs_btree_path *path,
  				  int level, __u64 *keyp, __u64 *ptrp)
  {
  	struct nilfs_btree_node *node;
  	int ncblk;
  
  	if (level < nilfs_btree_height(btree) - 1) {
  		node = nilfs_btree_get_nonroot_node(path, level);
  		ncblk = nilfs_btree_nchildren_per_block(btree);
  		nilfs_btree_node_delete(node, path[level].bp_index,
  					keyp, ptrp, ncblk);
  		if (!buffer_dirty(path[level].bp_bh))
  			mark_buffer_dirty(path[level].bp_bh);
  		if (path[level].bp_index == 0)
  			nilfs_btree_promote_key(btree, path, level + 1,
  				nilfs_btree_node_get_key(node, 0));
  	} else {
  		node = nilfs_btree_get_root(btree);
  		nilfs_btree_node_delete(node, path[level].bp_index,
  					keyp, ptrp,
  					NILFS_BTREE_ROOT_NCHILDREN_MAX);
  	}
  }
  
  static void nilfs_btree_borrow_left(struct nilfs_bmap *btree,
  				    struct nilfs_btree_path *path,
  				    int level, __u64 *keyp, __u64 *ptrp)
  {
  	struct nilfs_btree_node *node, *left;
  	int nchildren, lnchildren, n, ncblk;
  
  	nilfs_btree_do_delete(btree, path, level, keyp, ptrp);
  
  	node = nilfs_btree_get_nonroot_node(path, level);
  	left = nilfs_btree_get_sib_node(path, level);
  	nchildren = nilfs_btree_node_get_nchildren(node);
  	lnchildren = nilfs_btree_node_get_nchildren(left);
  	ncblk = nilfs_btree_nchildren_per_block(btree);
  
  	n = (nchildren + lnchildren) / 2 - nchildren;
  
  	nilfs_btree_node_move_right(left, node, n, ncblk, ncblk);
  
  	if (!buffer_dirty(path[level].bp_bh))
  		mark_buffer_dirty(path[level].bp_bh);
  	if (!buffer_dirty(path[level].bp_sib_bh))
  		mark_buffer_dirty(path[level].bp_sib_bh);
  
  	nilfs_btree_promote_key(btree, path, level + 1,
  				nilfs_btree_node_get_key(node, 0));
  
  	brelse(path[level].bp_sib_bh);
  	path[level].bp_sib_bh = NULL;
  	path[level].bp_index += n;
  }
  
  static void nilfs_btree_borrow_right(struct nilfs_bmap *btree,
  				     struct nilfs_btree_path *path,
  				     int level, __u64 *keyp, __u64 *ptrp)
  {
  	struct nilfs_btree_node *node, *right;
  	int nchildren, rnchildren, n, ncblk;
  
  	nilfs_btree_do_delete(btree, path, level, keyp, ptrp);
  
  	node = nilfs_btree_get_nonroot_node(path, level);
  	right = nilfs_btree_get_sib_node(path, level);
  	nchildren = nilfs_btree_node_get_nchildren(node);
  	rnchildren = nilfs_btree_node_get_nchildren(right);
  	ncblk = nilfs_btree_nchildren_per_block(btree);
  
  	n = (nchildren + rnchildren) / 2 - nchildren;
  
  	nilfs_btree_node_move_left(node, right, n, ncblk, ncblk);
  
  	if (!buffer_dirty(path[level].bp_bh))
  		mark_buffer_dirty(path[level].bp_bh);
  	if (!buffer_dirty(path[level].bp_sib_bh))
  		mark_buffer_dirty(path[level].bp_sib_bh);
  
  	path[level + 1].bp_index++;
  	nilfs_btree_promote_key(btree, path, level + 1,
  				nilfs_btree_node_get_key(right, 0));
  	path[level + 1].bp_index--;
  
  	brelse(path[level].bp_sib_bh);
  	path[level].bp_sib_bh = NULL;
  }
  
  static void nilfs_btree_concat_left(struct nilfs_bmap *btree,
  				    struct nilfs_btree_path *path,
  				    int level, __u64 *keyp, __u64 *ptrp)
  {
  	struct nilfs_btree_node *node, *left;
  	int n, ncblk;
  
  	nilfs_btree_do_delete(btree, path, level, keyp, ptrp);
  
  	node = nilfs_btree_get_nonroot_node(path, level);
  	left = nilfs_btree_get_sib_node(path, level);
  	ncblk = nilfs_btree_nchildren_per_block(btree);
  
  	n = nilfs_btree_node_get_nchildren(node);
  
  	nilfs_btree_node_move_left(left, node, n, ncblk, ncblk);
  
  	if (!buffer_dirty(path[level].bp_sib_bh))
  		mark_buffer_dirty(path[level].bp_sib_bh);
  
  	nilfs_btnode_delete(path[level].bp_bh);
  	path[level].bp_bh = path[level].bp_sib_bh;
  	path[level].bp_sib_bh = NULL;
  	path[level].bp_index += nilfs_btree_node_get_nchildren(left);
  }
  
  static void nilfs_btree_concat_right(struct nilfs_bmap *btree,
  				     struct nilfs_btree_path *path,
  				     int level, __u64 *keyp, __u64 *ptrp)
  {
  	struct nilfs_btree_node *node, *right;
  	int n, ncblk;
  
  	nilfs_btree_do_delete(btree, path, level, keyp, ptrp);
  
  	node = nilfs_btree_get_nonroot_node(path, level);
  	right = nilfs_btree_get_sib_node(path, level);
  	ncblk = nilfs_btree_nchildren_per_block(btree);
  
  	n = nilfs_btree_node_get_nchildren(right);
  
  	nilfs_btree_node_move_left(node, right, n, ncblk, ncblk);
  
  	if (!buffer_dirty(path[level].bp_bh))
  		mark_buffer_dirty(path[level].bp_bh);
  
  	nilfs_btnode_delete(path[level].bp_sib_bh);
  	path[level].bp_sib_bh = NULL;
  	path[level + 1].bp_index++;
  }
  
  static void nilfs_btree_shrink(struct nilfs_bmap *btree,
  			       struct nilfs_btree_path *path,
  			       int level, __u64 *keyp, __u64 *ptrp)
  {
  	struct nilfs_btree_node *root, *child;
  	int n, ncblk;
  
  	nilfs_btree_do_delete(btree, path, level, keyp, ptrp);
  
  	root = nilfs_btree_get_root(btree);
  	child = nilfs_btree_get_nonroot_node(path, level);
  	ncblk = nilfs_btree_nchildren_per_block(btree);
  
  	nilfs_btree_node_delete(root, 0, NULL, NULL,
  				NILFS_BTREE_ROOT_NCHILDREN_MAX);
  	nilfs_btree_node_set_level(root, level);
  	n = nilfs_btree_node_get_nchildren(child);
  	nilfs_btree_node_move_left(root, child, n,
  				   NILFS_BTREE_ROOT_NCHILDREN_MAX, ncblk);
  
  	nilfs_btnode_delete(path[level].bp_bh);
  	path[level].bp_bh = NULL;
  }
  
  static void nilfs_btree_nop(struct nilfs_bmap *btree,
  			    struct nilfs_btree_path *path,
  			    int level, __u64 *keyp, __u64 *ptrp)
  {
  }
  
  static int nilfs_btree_prepare_delete(struct nilfs_bmap *btree,
  				      struct nilfs_btree_path *path,
  				      int *levelp,
  				      struct nilfs_bmap_stats *stats,
  				      struct inode *dat)
  {
  	struct buffer_head *bh;
  	struct nilfs_btree_node *node, *parent, *sib;
  	__u64 sibptr;
  	int pindex, dindex, level, ncmin, ncmax, ncblk, ret;
  
  	ret = 0;
  	stats->bs_nblocks = 0;
  	ncmin = NILFS_BTREE_NODE_NCHILDREN_MIN(nilfs_btree_node_size(btree));
  	ncblk = nilfs_btree_nchildren_per_block(btree);
  
  	for (level = NILFS_BTREE_LEVEL_NODE_MIN, dindex = path[level].bp_index;
  	     level < nilfs_btree_height(btree) - 1;
  	     level++) {
  		node = nilfs_btree_get_nonroot_node(path, level);
  		path[level].bp_oldreq.bpr_ptr =
  			nilfs_btree_node_get_ptr(node, dindex, ncblk);
  		ret = nilfs_bmap_prepare_end_ptr(btree,
  						 &path[level].bp_oldreq, dat);
  		if (ret < 0)
  			goto err_out_child_node;
  
  		if (nilfs_btree_node_get_nchildren(node) > ncmin) {
  			path[level].bp_op = nilfs_btree_do_delete;
  			stats->bs_nblocks++;
  			goto out;
  		}
  
  		parent = nilfs_btree_get_node(btree, path, level + 1, &ncmax);
  		pindex = path[level + 1].bp_index;
  		dindex = pindex;
  
  		if (pindex > 0) {
  			/* left sibling */
  			sibptr = nilfs_btree_node_get_ptr(parent, pindex - 1,
  							  ncmax);
  			ret = nilfs_btree_get_block(btree, sibptr, &bh);
  			if (ret < 0)
  				goto err_out_curr_node;
  			sib = (struct nilfs_btree_node *)bh->b_data;
  			if (nilfs_btree_node_get_nchildren(sib) > ncmin) {
  				path[level].bp_sib_bh = bh;
  				path[level].bp_op = nilfs_btree_borrow_left;
  				stats->bs_nblocks++;
  				goto out;
  			} else {
  				path[level].bp_sib_bh = bh;
  				path[level].bp_op = nilfs_btree_concat_left;
  				stats->bs_nblocks++;
  				/* continue; */
  			}
  		} else if (pindex <
  			   nilfs_btree_node_get_nchildren(parent) - 1) {
  			/* right sibling */
  			sibptr = nilfs_btree_node_get_ptr(parent, pindex + 1,
  							  ncmax);
  			ret = nilfs_btree_get_block(btree, sibptr, &bh);
  			if (ret < 0)
  				goto err_out_curr_node;
  			sib = (struct nilfs_btree_node *)bh->b_data;
  			if (nilfs_btree_node_get_nchildren(sib) > ncmin) {
  				path[level].bp_sib_bh = bh;
  				path[level].bp_op = nilfs_btree_borrow_right;
  				stats->bs_nblocks++;
  				goto out;
  			} else {
  				path[level].bp_sib_bh = bh;
  				path[level].bp_op = nilfs_btree_concat_right;
  				stats->bs_nblocks++;
  				/*
  				 * When merging right sibling node
  				 * into the current node, pointer to
  				 * the right sibling node must be
  				 * terminated instead.  The adjustment
  				 * below is required for that.
  				 */
  				dindex = pindex + 1;
  				/* continue; */
  			}
  		} else {
  			/* no siblings */
  			/* the only child of the root node */
  			WARN_ON(level != nilfs_btree_height(btree) - 2);
  			if (nilfs_btree_node_get_nchildren(node) - 1 <=
  			    NILFS_BTREE_ROOT_NCHILDREN_MAX) {
  				path[level].bp_op = nilfs_btree_shrink;
  				stats->bs_nblocks += 2;
  				level++;
  				path[level].bp_op = nilfs_btree_nop;
  				goto shrink_root_child;
  			} else {
  				path[level].bp_op = nilfs_btree_do_delete;
  				stats->bs_nblocks++;
  				goto out;
  			}
  		}
  	}
  
  	/* child of the root node is deleted */
  	path[level].bp_op = nilfs_btree_do_delete;
  	stats->bs_nblocks++;
  
  shrink_root_child:
  	node = nilfs_btree_get_root(btree);
  	path[level].bp_oldreq.bpr_ptr =
  		nilfs_btree_node_get_ptr(node, dindex,
  					 NILFS_BTREE_ROOT_NCHILDREN_MAX);
  
  	ret = nilfs_bmap_prepare_end_ptr(btree, &path[level].bp_oldreq, dat);
  	if (ret < 0)
  		goto err_out_child_node;
  
  	/* success */
   out:
  	*levelp = level;
  	return ret;
  
  	/* error */
   err_out_curr_node:
  	nilfs_bmap_abort_end_ptr(btree, &path[level].bp_oldreq, dat);
   err_out_child_node:
  	for (level--; level >= NILFS_BTREE_LEVEL_NODE_MIN; level--) {
  		brelse(path[level].bp_sib_bh);
  		nilfs_bmap_abort_end_ptr(btree, &path[level].bp_oldreq, dat);
  	}
  	*levelp = level;
  	stats->bs_nblocks = 0;
  	return ret;
  }
  
  static void nilfs_btree_commit_delete(struct nilfs_bmap *btree,
  				      struct nilfs_btree_path *path,
  				      int maxlevel, struct inode *dat)
  {
  	int level;
  
  	for (level = NILFS_BTREE_LEVEL_NODE_MIN; level <= maxlevel; level++) {
  		nilfs_bmap_commit_end_ptr(btree, &path[level].bp_oldreq, dat);
  		path[level].bp_op(btree, path, level, NULL, NULL);
  	}
  
  	if (!nilfs_bmap_dirty(btree))
  		nilfs_bmap_set_dirty(btree);
  }
  
  static int nilfs_btree_delete(struct nilfs_bmap *btree, __u64 key)
  
  {
  	struct nilfs_btree_path *path;
  	struct nilfs_bmap_stats stats;
  	struct inode *dat;
  	int level, ret;
  
  	path = nilfs_btree_alloc_path();
  	if (path == NULL)
  		return -ENOMEM;
  
  	ret = nilfs_btree_do_lookup(btree, path, key, NULL,
  				    NILFS_BTREE_LEVEL_NODE_MIN, 0);
  	if (ret < 0)
  		goto out;
  
  
  	dat = NILFS_BMAP_USE_VBN(btree) ? nilfs_bmap_get_dat(btree) : NULL;
  
  	ret = nilfs_btree_prepare_delete(btree, path, &level, &stats, dat);
  	if (ret < 0)
  		goto out;
  	nilfs_btree_commit_delete(btree, path, level, dat);
  	nilfs_inode_sub_blocks(btree->b_inode, stats.bs_nblocks);
  
  out:
  	nilfs_btree_free_path(path);
  	return ret;
  }
  
  static int nilfs_btree_seek_key(const struct nilfs_bmap *btree, __u64 start,
  				__u64 *keyp)
  {
  	struct nilfs_btree_path *path;
  	const int minlevel = NILFS_BTREE_LEVEL_NODE_MIN;
  	int ret;
  
  	path = nilfs_btree_alloc_path();
  	if (!path)
  		return -ENOMEM;
  
  	ret = nilfs_btree_do_lookup(btree, path, start, NULL, minlevel, 0);
  	if (!ret)
  		*keyp = start;
  	else if (ret == -ENOENT)
  		ret = nilfs_btree_get_next_key(btree, path, minlevel, keyp);
  
  	nilfs_btree_free_path(path);
  	return ret;
  }
  
  static int nilfs_btree_last_key(const struct nilfs_bmap *btree, __u64 *keyp)
  {
  	struct nilfs_btree_path *path;
  	int ret;
  
  	path = nilfs_btree_alloc_path();
  	if (path == NULL)
  		return -ENOMEM;
  
  	ret = nilfs_btree_do_lookup_last(btree, path, keyp, NULL);
  
  	nilfs_btree_free_path(path);
  
  	return ret;
  }
  
  static int nilfs_btree_check_delete(struct nilfs_bmap *btree, __u64 key)
  {
  	struct buffer_head *bh;
  	struct nilfs_btree_node *root, *node;
  	__u64 maxkey, nextmaxkey;
  	__u64 ptr;
  	int nchildren, ret;
  
  	root = nilfs_btree_get_root(btree);
  	switch (nilfs_btree_height(btree)) {
  	case 2:
  		bh = NULL;
  		node = root;
  		break;
  	case 3:
  		nchildren = nilfs_btree_node_get_nchildren(root);
  		if (nchildren > 1)
  			return 0;
  		ptr = nilfs_btree_node_get_ptr(root, nchildren - 1,
  					       NILFS_BTREE_ROOT_NCHILDREN_MAX);
  		ret = nilfs_btree_get_block(btree, ptr, &bh);
  		if (ret < 0)
  			return ret;
  		node = (struct nilfs_btree_node *)bh->b_data;
  		break;
  	default:
  		return 0;
  	}
  
  	nchildren = nilfs_btree_node_get_nchildren(node);
  	maxkey = nilfs_btree_node_get_key(node, nchildren - 1);
  	nextmaxkey = (nchildren > 1) ?
  		nilfs_btree_node_get_key(node, nchildren - 2) : 0;
  	if (bh != NULL)
  		brelse(bh);
  
  	return (maxkey == key) && (nextmaxkey < NILFS_BMAP_LARGE_LOW);
  }
  
  static int nilfs_btree_gather_data(struct nilfs_bmap *btree,
  				   __u64 *keys, __u64 *ptrs, int nitems)
  {
  	struct buffer_head *bh;
  	struct nilfs_btree_node *node, *root;
  	__le64 *dkeys;
  	__le64 *dptrs;
  	__u64 ptr;
  	int nchildren, ncmax, i, ret;
  
  	root = nilfs_btree_get_root(btree);
  	switch (nilfs_btree_height(btree)) {
  	case 2:
  		bh = NULL;
  		node = root;
  		ncmax = NILFS_BTREE_ROOT_NCHILDREN_MAX;
  		break;
  	case 3:
  		nchildren = nilfs_btree_node_get_nchildren(root);
  		WARN_ON(nchildren > 1);
  		ptr = nilfs_btree_node_get_ptr(root, nchildren - 1,
  					       NILFS_BTREE_ROOT_NCHILDREN_MAX);
  		ret = nilfs_btree_get_block(btree, ptr, &bh);
  		if (ret < 0)
  			return ret;
  		node = (struct nilfs_btree_node *)bh->b_data;
  		ncmax = nilfs_btree_nchildren_per_block(btree);
  		break;
  	default:
  		node = NULL;
  		return -EINVAL;
  	}
  
  	nchildren = nilfs_btree_node_get_nchildren(node);
  	if (nchildren < nitems)
  		nitems = nchildren;
  	dkeys = nilfs_btree_node_dkeys(node);
  	dptrs = nilfs_btree_node_dptrs(node, ncmax);
  	for (i = 0; i < nitems; i++) {
  		keys[i] = le64_to_cpu(dkeys[i]);
  		ptrs[i] = le64_to_cpu(dptrs[i]);
  	}
  
  	if (bh != NULL)
  		brelse(bh);
  
  	return nitems;
  }
  
  static int
  nilfs_btree_prepare_convert_and_insert(struct nilfs_bmap *btree, __u64 key,
  				       union nilfs_bmap_ptr_req *dreq,
  				       union nilfs_bmap_ptr_req *nreq,
  				       struct buffer_head **bhp,
  				       struct nilfs_bmap_stats *stats)
  {
  	struct buffer_head *bh;
  	struct inode *dat = NULL;
  	int ret;
  
  	stats->bs_nblocks = 0;
  
  	/* for data */
  	/* cannot find near ptr */
  	if (NILFS_BMAP_USE_VBN(btree)) {
  		dreq->bpr_ptr = nilfs_btree_find_target_v(btree, NULL, key);
  		dat = nilfs_bmap_get_dat(btree);
  	}
  
  	ret = nilfs_bmap_prepare_alloc_ptr(btree, dreq, dat);
  	if (ret < 0)
  		return ret;
  
  	*bhp = NULL;
  	stats->bs_nblocks++;
  	if (nreq != NULL) {
  		nreq->bpr_ptr = dreq->bpr_ptr + 1;
  		ret = nilfs_bmap_prepare_alloc_ptr(btree, nreq, dat);
  		if (ret < 0)
  			goto err_out_dreq;
  
  		ret = nilfs_btree_get_new_block(btree, nreq->bpr_ptr, &bh);
  		if (ret < 0)
  			goto err_out_nreq;
  
  		*bhp = bh;
  		stats->bs_nblocks++;
  	}
  
  	/* success */
  	return 0;
  
  	/* error */
   err_out_nreq:
  	nilfs_bmap_abort_alloc_ptr(btree, nreq, dat);
   err_out_dreq:
  	nilfs_bmap_abort_alloc_ptr(btree, dreq, dat);
  	stats->bs_nblocks = 0;
  	return ret;
  
  }
  
  static void
  nilfs_btree_commit_convert_and_insert(struct nilfs_bmap *btree,
  				      __u64 key, __u64 ptr,
  				      const __u64 *keys, const __u64 *ptrs,
  				      int n,
  				      union nilfs_bmap_ptr_req *dreq,
  				      union nilfs_bmap_ptr_req *nreq,
  				      struct buffer_head *bh)
  {
  	struct nilfs_btree_node *node;
  	struct inode *dat;
  	__u64 tmpptr;
  	int ncblk;
  
  	/* free resources */
  	if (btree->b_ops->bop_clear != NULL)
  		btree->b_ops->bop_clear(btree);
  
  	/* ptr must be a pointer to a buffer head. */
  	set_buffer_nilfs_volatile((struct buffer_head *)((unsigned long)ptr));
  
  	/* convert and insert */
  	dat = NILFS_BMAP_USE_VBN(btree) ? nilfs_bmap_get_dat(btree) : NULL;
  	__nilfs_btree_init(btree);
  	if (nreq != NULL) {
  		nilfs_bmap_commit_alloc_ptr(btree, dreq, dat);
  		nilfs_bmap_commit_alloc_ptr(btree, nreq, dat);
  
  		/* create child node at level 1 */
  		node = (struct nilfs_btree_node *)bh->b_data;
  		ncblk = nilfs_btree_nchildren_per_block(btree);
  		nilfs_btree_node_init(node, 0, 1, n, ncblk, keys, ptrs);
  		nilfs_btree_node_insert(node, n, key, dreq->bpr_ptr, ncblk);
  		if (!buffer_dirty(bh))
  			mark_buffer_dirty(bh);
  		if (!nilfs_bmap_dirty(btree))
  			nilfs_bmap_set_dirty(btree);
  
  		brelse(bh);
  
  		/* create root node at level 2 */
  		node = nilfs_btree_get_root(btree);
  		tmpptr = nreq->bpr_ptr;
  		nilfs_btree_node_init(node, NILFS_BTREE_NODE_ROOT, 2, 1,
  				      NILFS_BTREE_ROOT_NCHILDREN_MAX,
  				      &keys[0], &tmpptr);
  	} else {
  		nilfs_bmap_commit_alloc_ptr(btree, dreq, dat);
  
  		/* create root node at level 1 */
  		node = nilfs_btree_get_root(btree);
  		nilfs_btree_node_init(node, NILFS_BTREE_NODE_ROOT, 1, n,
  				      NILFS_BTREE_ROOT_NCHILDREN_MAX,
  				      keys, ptrs);
  		nilfs_btree_node_insert(node, n, key, dreq->bpr_ptr,
  					NILFS_BTREE_ROOT_NCHILDREN_MAX);
  		if (!nilfs_bmap_dirty(btree))
  			nilfs_bmap_set_dirty(btree);
  	}
  
  	if (NILFS_BMAP_USE_VBN(btree))
  		nilfs_bmap_set_target_v(btree, key, dreq->bpr_ptr);
  }
  
  /**
   * nilfs_btree_convert_and_insert -
   * @bmap:
   * @key:
   * @ptr:
   * @keys:
   * @ptrs:
   * @n:
   */
  int nilfs_btree_convert_and_insert(struct nilfs_bmap *btree,
  				   __u64 key, __u64 ptr,
  				   const __u64 *keys, const __u64 *ptrs, int n)
  {
  	struct buffer_head *bh = NULL;
  	union nilfs_bmap_ptr_req dreq, nreq, *di, *ni;
  	struct nilfs_bmap_stats stats;
  	int ret;
  
  	if (n + 1 <= NILFS_BTREE_ROOT_NCHILDREN_MAX) {
  		di = &dreq;
  		ni = NULL;
  	} else if ((n + 1) <= NILFS_BTREE_NODE_NCHILDREN_MAX(
  			   nilfs_btree_node_size(btree))) {
  		di = &dreq;
  		ni = &nreq;
  	} else {
  		di = NULL;
  		ni = NULL;
  		BUG();
  	}
  
  	ret = nilfs_btree_prepare_convert_and_insert(btree, key, di, ni, &bh,
  						     &stats);
  	if (ret < 0)
  		return ret;
  	nilfs_btree_commit_convert_and_insert(btree, key, ptr, keys, ptrs, n,
  					      di, ni, bh);
  	nilfs_inode_add_blocks(btree->b_inode, stats.bs_nblocks);
  	return 0;
  }
  
  static int nilfs_btree_propagate_p(struct nilfs_bmap *btree,
  				   struct nilfs_btree_path *path,
  				   int level,
  				   struct buffer_head *bh)
  {
  	while ((++level < nilfs_btree_height(btree) - 1) &&
  	       !buffer_dirty(path[level].bp_bh))
  		mark_buffer_dirty(path[level].bp_bh);
  
  	return 0;
  }
  
  static int nilfs_btree_prepare_update_v(struct nilfs_bmap *btree,
  					struct nilfs_btree_path *path,
  					int level, struct inode *dat)
  {
  	struct nilfs_btree_node *parent;
  	int ncmax, ret;
  
  	parent = nilfs_btree_get_node(btree, path, level + 1, &ncmax);
  	path[level].bp_oldreq.bpr_ptr =
  		nilfs_btree_node_get_ptr(parent, path[level + 1].bp_index,
  					 ncmax);
  	path[level].bp_newreq.bpr_ptr = path[level].bp_oldreq.bpr_ptr + 1;
  	ret = nilfs_dat_prepare_update(dat, &path[level].bp_oldreq.bpr_req,
  				       &path[level].bp_newreq.bpr_req);
  	if (ret < 0)
  		return ret;
  
  	if (buffer_nilfs_node(path[level].bp_bh)) {
  		path[level].bp_ctxt.oldkey = path[level].bp_oldreq.bpr_ptr;
  		path[level].bp_ctxt.newkey = path[level].bp_newreq.bpr_ptr;
  		path[level].bp_ctxt.bh = path[level].bp_bh;
  		ret = nilfs_btnode_prepare_change_key(
  			&NILFS_BMAP_I(btree)->i_btnode_cache,
  			&path[level].bp_ctxt);
  		if (ret < 0) {
  			nilfs_dat_abort_update(dat,
  					       &path[level].bp_oldreq.bpr_req,
  					       &path[level].bp_newreq.bpr_req);
  			return ret;
  		}
  	}
  
  	return 0;
  }
  
  static void nilfs_btree_commit_update_v(struct nilfs_bmap *btree,
  					struct nilfs_btree_path *path,
  					int level, struct inode *dat)
  {
  	struct nilfs_btree_node *parent;
  	int ncmax;
  
  	nilfs_dat_commit_update(dat, &path[level].bp_oldreq.bpr_req,
  				&path[level].bp_newreq.bpr_req,
  				btree->b_ptr_type == NILFS_BMAP_PTR_VS);
  
  	if (buffer_nilfs_node(path[level].bp_bh)) {
  		nilfs_btnode_commit_change_key(
  			&NILFS_BMAP_I(btree)->i_btnode_cache,
  			&path[level].bp_ctxt);
  		path[level].bp_bh = path[level].bp_ctxt.bh;
  	}
  	set_buffer_nilfs_volatile(path[level].bp_bh);
  
  	parent = nilfs_btree_get_node(btree, path, level + 1, &ncmax);
  	nilfs_btree_node_set_ptr(parent, path[level + 1].bp_index,
  				 path[level].bp_newreq.bpr_ptr, ncmax);
  }
  
  static void nilfs_btree_abort_update_v(struct nilfs_bmap *btree,
  				       struct nilfs_btree_path *path,
  				       int level, struct inode *dat)
  {
  	nilfs_dat_abort_update(dat, &path[level].bp_oldreq.bpr_req,
  			       &path[level].bp_newreq.bpr_req);
  	if (buffer_nilfs_node(path[level].bp_bh))
  		nilfs_btnode_abort_change_key(
  			&NILFS_BMAP_I(btree)->i_btnode_cache,
  			&path[level].bp_ctxt);
  }
  
  static int nilfs_btree_prepare_propagate_v(struct nilfs_bmap *btree,
  					   struct nilfs_btree_path *path,
  					   int minlevel, int *maxlevelp,
  					   struct inode *dat)
  {
  	int level, ret;
  
  	level = minlevel;
  	if (!buffer_nilfs_volatile(path[level].bp_bh)) {
  		ret = nilfs_btree_prepare_update_v(btree, path, level, dat);
  		if (ret < 0)
  			return ret;
  	}
  	while ((++level < nilfs_btree_height(btree) - 1) &&
  	       !buffer_dirty(path[level].bp_bh)) {
  
  		WARN_ON(buffer_nilfs_volatile(path[level].bp_bh));
  		ret = nilfs_btree_prepare_update_v(btree, path, level, dat);
  		if (ret < 0)
  			goto out;
  	}
  
  	/* success */
  	*maxlevelp = level - 1;
  	return 0;
  
  	/* error */
   out:
  	while (--level > minlevel)
  		nilfs_btree_abort_update_v(btree, path, level, dat);
  	if (!buffer_nilfs_volatile(path[level].bp_bh))
  		nilfs_btree_abort_update_v(btree, path, level, dat);
  	return ret;
  }
  
  static void nilfs_btree_commit_propagate_v(struct nilfs_bmap *btree,
  					   struct nilfs_btree_path *path,
  					   int minlevel, int maxlevel,
  					   struct buffer_head *bh,
  					   struct inode *dat)
  {
  	int level;
  
  	if (!buffer_nilfs_volatile(path[minlevel].bp_bh))
  		nilfs_btree_commit_update_v(btree, path, minlevel, dat);
  
  	for (level = minlevel + 1; level <= maxlevel; level++)
  		nilfs_btree_commit_update_v(btree, path, level, dat);
  }
  
  static int nilfs_btree_propagate_v(struct nilfs_bmap *btree,
  				   struct nilfs_btree_path *path,
  				   int level, struct buffer_head *bh)
  {
  	int maxlevel = 0, ret;
  	struct nilfs_btree_node *parent;
  	struct inode *dat = nilfs_bmap_get_dat(btree);
  	__u64 ptr;
  	int ncmax;
  
  	get_bh(bh);
  	path[level].bp_bh = bh;
  	ret = nilfs_btree_prepare_propagate_v(btree, path, level, &maxlevel,
  					      dat);
  	if (ret < 0)
  		goto out;
  
  	if (buffer_nilfs_volatile(path[level].bp_bh)) {
  		parent = nilfs_btree_get_node(btree, path, level + 1, &ncmax);
  		ptr = nilfs_btree_node_get_ptr(parent,
  					       path[level + 1].bp_index,
  					       ncmax);
  		ret = nilfs_dat_mark_dirty(dat, ptr);
  		if (ret < 0)
  			goto out;
  	}
  
  	nilfs_btree_commit_propagate_v(btree, path, level, maxlevel, bh, dat);
  
   out:
  	brelse(path[level].bp_bh);
  	path[level].bp_bh = NULL;
  	return ret;
  }
  
  static int nilfs_btree_propagate(struct nilfs_bmap *btree,
  				 struct buffer_head *bh)
  {
  	struct nilfs_btree_path *path;
  	struct nilfs_btree_node *node;
  	__u64 key;
  	int level, ret;
  
  	WARN_ON(!buffer_dirty(bh));
  
  	path = nilfs_btree_alloc_path();
  	if (path == NULL)
  		return -ENOMEM;
  
  	if (buffer_nilfs_node(bh)) {
  		node = (struct nilfs_btree_node *)bh->b_data;
  		key = nilfs_btree_node_get_key(node, 0);
  		level = nilfs_btree_node_get_level(node);
  	} else {
  		key = nilfs_bmap_data_get_key(btree, bh);
  		level = NILFS_BTREE_LEVEL_DATA;
  	}
  
  	ret = nilfs_btree_do_lookup(btree, path, key, NULL, level + 1, 0);
  	if (ret < 0) {
  		if (unlikely(ret == -ENOENT))
  			nilfs_crit(btree->b_inode->i_sb,
  				   "writing node/leaf block does not appear in b-tree (ino=%lu) at key=%llu, level=%d",
  				   btree->b_inode->i_ino,
  				   (unsigned long long)key, level);
  		goto out;
  	}
  
  	ret = NILFS_BMAP_USE_VBN(btree) ?
  		nilfs_btree_propagate_v(btree, path, level, bh) :
  		nilfs_btree_propagate_p(btree, path, level, bh);
  
   out:
  	nilfs_btree_free_path(path);
  
  	return ret;
  }
  
  static int nilfs_btree_propagate_gc(struct nilfs_bmap *btree,
  				    struct buffer_head *bh)
  {
  	return nilfs_dat_mark_dirty(nilfs_bmap_get_dat(btree), bh->b_blocknr);
  }
  
  static void nilfs_btree_add_dirty_buffer(struct nilfs_bmap *btree,
  					 struct list_head *lists,
  					 struct buffer_head *bh)
  {
  	struct list_head *head;
  	struct buffer_head *cbh;
  	struct nilfs_btree_node *node, *cnode;
  	__u64 key, ckey;
  	int level;
  
  	get_bh(bh);
  	node = (struct nilfs_btree_node *)bh->b_data;
  	key = nilfs_btree_node_get_key(node, 0);
  	level = nilfs_btree_node_get_level(node);
  	if (level < NILFS_BTREE_LEVEL_NODE_MIN ||
  	    level >= NILFS_BTREE_LEVEL_MAX) {
  		dump_stack();
  		nilfs_warn(btree->b_inode->i_sb,
  			   "invalid btree level: %d (key=%llu, ino=%lu, blocknr=%llu)",
  			   level, (unsigned long long)key,
  			   btree->b_inode->i_ino,
  			   (unsigned long long)bh->b_blocknr);
  		return;
  	}
  
  	list_for_each(head, &lists[level]) {
  		cbh = list_entry(head, struct buffer_head, b_assoc_buffers);
  		cnode = (struct nilfs_btree_node *)cbh->b_data;
  		ckey = nilfs_btree_node_get_key(cnode, 0);
  		if (key < ckey)
  			break;
  	}
  	list_add_tail(&bh->b_assoc_buffers, head);
  }
  
  static void nilfs_btree_lookup_dirty_buffers(struct nilfs_bmap *btree,
  					     struct list_head *listp)
  {
  	struct address_space *btcache = &NILFS_BMAP_I(btree)->i_btnode_cache;
  	struct list_head lists[NILFS_BTREE_LEVEL_MAX];
  	struct pagevec pvec;
  	struct buffer_head *bh, *head;
  	pgoff_t index = 0;
  	int level, i;
  
  	for (level = NILFS_BTREE_LEVEL_NODE_MIN;
  	     level < NILFS_BTREE_LEVEL_MAX;
  	     level++)
  		INIT_LIST_HEAD(&lists[level]);
  
  	pagevec_init(&pvec);
  
  	while (pagevec_lookup_tag(&pvec, btcache, &index,
  					PAGECACHE_TAG_DIRTY)) {
  		for (i = 0; i < pagevec_count(&pvec); i++) {
  			bh = head = page_buffers(pvec.pages[i]);
  			do {
  				if (buffer_dirty(bh))
  					nilfs_btree_add_dirty_buffer(btree,
  								     lists, bh);
  			} while ((bh = bh->b_this_page) != head);
  		}
  		pagevec_release(&pvec);
  		cond_resched();
  	}
  
  	for (level = NILFS_BTREE_LEVEL_NODE_MIN;
  	     level < NILFS_BTREE_LEVEL_MAX;
  	     level++)
  		list_splice_tail(&lists[level], listp);
  }
  
  static int nilfs_btree_assign_p(struct nilfs_bmap *btree,
  				struct nilfs_btree_path *path,
  				int level,
  				struct buffer_head **bh,
  				sector_t blocknr,
  				union nilfs_binfo *binfo)
  {
  	struct nilfs_btree_node *parent;
  	__u64 key;
  	__u64 ptr;
  	int ncmax, ret;
  
  	parent = nilfs_btree_get_node(btree, path, level + 1, &ncmax);
  	ptr = nilfs_btree_node_get_ptr(parent, path[level + 1].bp_index,
  				       ncmax);
  	if (buffer_nilfs_node(*bh)) {
  		path[level].bp_ctxt.oldkey = ptr;
  		path[level].bp_ctxt.newkey = blocknr;
  		path[level].bp_ctxt.bh = *bh;
  		ret = nilfs_btnode_prepare_change_key(
  			&NILFS_BMAP_I(btree)->i_btnode_cache,
  			&path[level].bp_ctxt);
  		if (ret < 0)
  			return ret;
  		nilfs_btnode_commit_change_key(
  			&NILFS_BMAP_I(btree)->i_btnode_cache,
  			&path[level].bp_ctxt);
  		*bh = path[level].bp_ctxt.bh;
  	}
  
  	nilfs_btree_node_set_ptr(parent, path[level + 1].bp_index, blocknr,
  				 ncmax);
  
  	key = nilfs_btree_node_get_key(parent, path[level + 1].bp_index);
  	/* on-disk format */
  	binfo->bi_dat.bi_blkoff = cpu_to_le64(key);
  	binfo->bi_dat.bi_level = level;
  
  	return 0;
  }
  
  static int nilfs_btree_assign_v(struct nilfs_bmap *btree,
  				struct nilfs_btree_path *path,
  				int level,
  				struct buffer_head **bh,
  				sector_t blocknr,
  				union nilfs_binfo *binfo)
  {
  	struct nilfs_btree_node *parent;
  	struct inode *dat = nilfs_bmap_get_dat(btree);
  	__u64 key;
  	__u64 ptr;
  	union nilfs_bmap_ptr_req req;
  	int ncmax, ret;
  
  	parent = nilfs_btree_get_node(btree, path, level + 1, &ncmax);
  	ptr = nilfs_btree_node_get_ptr(parent, path[level + 1].bp_index,
  				       ncmax);
  	req.bpr_ptr = ptr;
  	ret = nilfs_dat_prepare_start(dat, &req.bpr_req);
  	if (ret < 0)
  		return ret;
  	nilfs_dat_commit_start(dat, &req.bpr_req, blocknr);
  
  	key = nilfs_btree_node_get_key(parent, path[level + 1].bp_index);
  	/* on-disk format */
  	binfo->bi_v.bi_vblocknr = cpu_to_le64(ptr);
  	binfo->bi_v.bi_blkoff = cpu_to_le64(key);
  
  	return 0;
  }
  
  static int nilfs_btree_assign(struct nilfs_bmap *btree,
  			      struct buffer_head **bh,
  			      sector_t blocknr,
  			      union nilfs_binfo *binfo)
  {
  	struct nilfs_btree_path *path;
  	struct nilfs_btree_node *node;
  	__u64 key;
  	int level, ret;
  
  	path = nilfs_btree_alloc_path();
  	if (path == NULL)
  		return -ENOMEM;
  
  	if (buffer_nilfs_node(*bh)) {
  		node = (struct nilfs_btree_node *)(*bh)->b_data;
  		key = nilfs_btree_node_get_key(node, 0);
  		level = nilfs_btree_node_get_level(node);
  	} else {
  		key = nilfs_bmap_data_get_key(btree, *bh);
  		level = NILFS_BTREE_LEVEL_DATA;
  	}
  
  	ret = nilfs_btree_do_lookup(btree, path, key, NULL, level + 1, 0);
  	if (ret < 0) {
  		WARN_ON(ret == -ENOENT);
  		goto out;
  	}
  
  	ret = NILFS_BMAP_USE_VBN(btree) ?
  		nilfs_btree_assign_v(btree, path, level, bh, blocknr, binfo) :
  		nilfs_btree_assign_p(btree, path, level, bh, blocknr, binfo);
  
   out:
  	nilfs_btree_free_path(path);
  
  	return ret;
  }
  
  static int nilfs_btree_assign_gc(struct nilfs_bmap *btree,
  				 struct buffer_head **bh,
  				 sector_t blocknr,
  				 union nilfs_binfo *binfo)
  {
  	struct nilfs_btree_node *node;
  	__u64 key;
  	int ret;
  
  	ret = nilfs_dat_move(nilfs_bmap_get_dat(btree), (*bh)->b_blocknr,
  			     blocknr);
  	if (ret < 0)
  		return ret;
  
  	if (buffer_nilfs_node(*bh)) {
  		node = (struct nilfs_btree_node *)(*bh)->b_data;
  		key = nilfs_btree_node_get_key(node, 0);
  	} else
  		key = nilfs_bmap_data_get_key(btree, *bh);
  
  	/* on-disk format */
  	binfo->bi_v.bi_vblocknr = cpu_to_le64((*bh)->b_blocknr);
  	binfo->bi_v.bi_blkoff = cpu_to_le64(key);
  
  	return 0;
  }
  
  static int nilfs_btree_mark(struct nilfs_bmap *btree, __u64 key, int level)
  {
  	struct buffer_head *bh;
  	struct nilfs_btree_path *path;
  	__u64 ptr;
  	int ret;
  
  	path = nilfs_btree_alloc_path();
  	if (path == NULL)
  		return -ENOMEM;
  
  	ret = nilfs_btree_do_lookup(btree, path, key, &ptr, level + 1, 0);
  	if (ret < 0) {
  		WARN_ON(ret == -ENOENT);
  		goto out;
  	}
  	ret = nilfs_btree_get_block(btree, ptr, &bh);
  	if (ret < 0) {
  		WARN_ON(ret == -ENOENT);
  		goto out;
  	}
  
  	if (!buffer_dirty(bh))
  		mark_buffer_dirty(bh);
  	brelse(bh);
  	if (!nilfs_bmap_dirty(btree))
  		nilfs_bmap_set_dirty(btree);
  
   out:
  	nilfs_btree_free_path(path);
  	return ret;
  }
  
  static const struct nilfs_bmap_operations nilfs_btree_ops = {
  	.bop_lookup		=	nilfs_btree_lookup,
  	.bop_lookup_contig	=	nilfs_btree_lookup_contig,
  	.bop_insert		=	nilfs_btree_insert,
  	.bop_delete		=	nilfs_btree_delete,
  	.bop_clear		=	NULL,
  
  	.bop_propagate		=	nilfs_btree_propagate,
  
  	.bop_lookup_dirty_buffers =	nilfs_btree_lookup_dirty_buffers,
  
  	.bop_assign		=	nilfs_btree_assign,
  	.bop_mark		=	nilfs_btree_mark,
  
  	.bop_seek_key		=	nilfs_btree_seek_key,
  	.bop_last_key		=	nilfs_btree_last_key,
  
  	.bop_check_insert	=	NULL,
  	.bop_check_delete	=	nilfs_btree_check_delete,
  	.bop_gather_data	=	nilfs_btree_gather_data,
  };
  
  static const struct nilfs_bmap_operations nilfs_btree_ops_gc = {
  	.bop_lookup		=	NULL,
  	.bop_lookup_contig	=	NULL,
  	.bop_insert		=	NULL,
  	.bop_delete		=	NULL,
  	.bop_clear		=	NULL,
  
  	.bop_propagate		=	nilfs_btree_propagate_gc,
  
  	.bop_lookup_dirty_buffers =	nilfs_btree_lookup_dirty_buffers,
  
  	.bop_assign		=	nilfs_btree_assign_gc,
  	.bop_mark		=	NULL,
  
  	.bop_seek_key		=	NULL,
  	.bop_last_key		=	NULL,
  
  	.bop_check_insert	=	NULL,
  	.bop_check_delete	=	NULL,
  	.bop_gather_data	=	NULL,
  };
  
  static void __nilfs_btree_init(struct nilfs_bmap *bmap)
  {
  	bmap->b_ops = &nilfs_btree_ops;
  	bmap->b_nchildren_per_block =
  		NILFS_BTREE_NODE_NCHILDREN_MAX(nilfs_btree_node_size(bmap));
  }
  
  int nilfs_btree_init(struct nilfs_bmap *bmap)
  {
  	int ret = 0;
  
  	__nilfs_btree_init(bmap);
  
  	if (nilfs_btree_root_broken(nilfs_btree_get_root(bmap), bmap->b_inode))
  		ret = -EIO;
  	return ret;
  }
  
  void nilfs_btree_init_gc(struct nilfs_bmap *bmap)
  {
  	bmap->b_ops = &nilfs_btree_ops_gc;
  	bmap->b_nchildren_per_block =
  		NILFS_BTREE_NODE_NCHILDREN_MAX(nilfs_btree_node_size(bmap));
  }
  